Wafer grinding using an adhesive gel material

ABSTRACT

Methods for semiconductor wafer grinding using an adhesive gel material are described herein.

TECHNICAL FIELD & BACKGROUND

The present disclosure is related to the field of semiconductor device manufacturing and packaging. More specifically but not exclusively, the present disclosure is related to semiconductor wafer grinding using an adhesive gel material.

Semiconductor wafers are usually thinned prior to the assembly of individual semiconductor devices. Such thinning is often accomplished by wafer grinding or “backgrinding” since it is usually done by mechanically grinding a lower surface (i.e., back) of a wafer. A conventional method of protection is the application of a “backgrind” tape or grinding protection tape over an active or upper surface of the wafer to protect integrated circuits or other surface structures on the wafer during grinding. Among the disadvantages of using such tape is that tape selection for various wafer types (for example, wire bond, flip chip and alternative bumped method wafer types) can be time-consuming and complicated. Furthermore, wafer taping and de-taping adds expense and processing time to wafer packaging and may damage a wafer surface by leaving behind adhesive residue and damaged or missing wafer bumps when the tape is removed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described by way of exemplary embodiments, but not limitations, illustrated in the accompanying drawings in which like references denote similar elements, and in which:

FIGS. 1 and 2 illustrate two prior art semiconductor wafer grinding and dicing methods;

FIG. 3 illustrates a cross-sectional view of a prior art vacuum chuck used in the prior art semiconductor wafer grinding and dicing methods of FIGS. 1 and 2;

FIGS. 4 a and 4 b illustrate enlarged cross-sectional views of a wafer on a platform according to embodiments of the invention.

FIGS. 5 and 6 illustrate cross-sectional views of the vacuum chuck of FIG. 3 and placement of a wafer thereon in accordance with embodiments of the invention;

FIGS. 7 and 8 illustrate methods for semiconductor wafer grinding and dicing in accordance with embodiments of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of the present invention include, but are not limited to, methods for semiconductor wafer grinding using an adhesive gel material.

Various aspects of the illustrative embodiments will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that the present invention may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the illustrative embodiments. However, it will be apparent to one skilled in the art that embodiments of the present invention may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative embodiments.

Various operations will be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the present invention, however, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.

The phrase “in one embodiment” is used repeatedly. The phrase generally does not refer to the same embodiment, however, it may. The terms “comprising”, “having” and “including” are synonymous, unless the context dictates otherwise.

Embodiments of a method for semiconductor wafer grinding using an adhesive gel material are described herein. For simplicity and clarity of explanation, various embodiments of the invention are shown in the figures according to various views. It is to be appreciated that such views are merely illustrative and are not necessarily drawn to scale or to the exact shape. Furthermore, it is to be appreciated that the actual devices utilizing principles of the invention may vary in shape, size, configuration, contour, and the like, other than what is shown in the figures, due to different manufacturing processes, equipment, design tolerances, or other practical considerations that result in variations from one semiconductor device to another.

FIGS. 1 and 2 illustrate example prior art semiconductor wafer grinding and dicing methods. In FIG. 1, a prior art semiconductor wafer grind-before-dice method is shown. Backgrind tape or grinding protection tape 102 is first taped to a semiconductor wafer 104 (hereinafter, simply “wafer”) to protect integrated circuits or other surface structures formed on an active or upper surface 105 of wafer 104. With grinding protection tape 102 attached to upper surface 105 of wafer 104, wafer 104 may then be mounted, face down, to a surface or platform 114 of vacuum chuck 106. Vacuum chuck 106 may apply a suction or vacuum to hold wafer 104 and grinding protection tape 102 which is adhesively attached to wafer 104, to vacuum chuck 106. Once wafer 104 is suctioned face-down to vacuum chuck 106, wafer 104 may now be ready to be thinned by removing material from a back side or a lower surface 109 (untaped side) of wafer 104 by a grinding chuck 108.

After the grinding process, grinding protection tape 102 may be removed or de-taped from upper surface 105 of wafer 104. Wafer 104 may then be mounted with a wafer mount tape 112 applied to lower surface 109 of wafer 104. Wafer 104 may then be singulated or diced at 116 into separate integrated circuit die or a plurality of integrated circuit die.

Another variation of the above prior art process can be used. FIG. 2 illustrates a prior art method called dice-before-grind (“DBG”), which moves dicing to the start of the process and eliminates the handling of very thin ground wafers as a whole. In FIG. 2, wafer 104 may be diced at 116 to a depth slightly deeper than a final desired wafer thickness. Grinding protection tape 102 may be attached to upper surface 105 of wafer 104. As in FIG. 1, wafer 104 may then be mounted, face down, to platform 114 of vacuum chuck 106 so that lower surface 109 may be thinned by grinding chuck 108. Then, lower surface 109 of wafer 104 may be mounted with wafer mount tape 112 and grinding protection tape 102 may then be removed.

FIG. 3 illustrates a cross-sectional view of prior art vacuum chuck 106 of FIGS. 1 and 2. Vacuum chuck 106 may include a porous material 304 through which air flow or a vacuum 308 may be applied. Platform 114 of vacuum chuck 106 may generally include a surface that, although porous, may be hard and may damage wafer 104 if grinding protection tape 102 is not used to help absorb some of the grinding pressure, force, and vibration.

FIGS. 4 a and 4 b illustrate embodiments wherein an adhesive gel material or gel material 404 may rely on a changing surface contact area between wafer 104 and gel material 404 to hold or, in the alternative, release wafer 104. As illustrated, for the embodiment, FIG. 4 a shows that gel material 404 may include a gel membrane 410. For the embodiment, gel material 404 may include adhesive properties to allow gel material 404 to act as a bonding agent between two surfaces when surface contact area is substantial. Thus, as shown in the embodiment of FIG. 4 a, substantial surface contact between gel membrane 410 of gel material 404 and upper surface 105 of wafer 104 may hold wafer 104 in position on a platform 114 during grinding. Platform 114 may be a surface of a vacuum chuck in one embodiment. Gel material 404 may be similar to gel material used in some instances for packing and shipping of wafers in an embodiment. For example, in one embodiment, gel material 404 may be a material such as for example, Gel-Pak™, available from Gel-Pak, Inc., located in Hayward, Calif., U.S.A.

In various embodiments, upper surface 105 of wafer 104 may include surface structures including electronic circuitry and related devices. Because gel material 404 may be of a semi-solid or semi-fluid nature, gel material 404 may be able to fill in one or more recesses or depressions of wafer 104, therefore increasing surface area contact while increasing adhesion and cushioning properties. Platform 114 may include a vacuum in the embodiment and is turned off in FIG. 4 a.

In FIG. 4 b, in order to allow gel material 404 to release wafer 104 from platform 114 after grinding is finished, the vacuum may be applied to gel material 404 in the embodiment. As illustrated by depressions in gel membrane 410, surface contact between wafer 104 and gel material 404 may be reduced or minimized as the vacuum draws gel membrane 410 away from inverted upper surface 105 of wafer 104 and toward platform 114 to lessen a holding strength of gel material 404. Note that in the embodiment, gel material 404 may include semi-solid particles 406 to prevent total or substantial collapse of gel membrane 410 to reduce surface contact between gel membrane 410 and upper surface 105 to release wafer 104 from platform 114 when the vacuum is activated. Note that for the embodiment, semi-solid particles 406 may be comprised of any organic, inorganic, or synthetic semi-solid material suitable to prevent total or substantial collapse of gel membrane 410 when the vacuum is activated. In one embodiment, for example, semi-solid particles 406 may be comprised of a similar material to gel material 404 but with a more solid composition. In other embodiments, semi-solid particles 406 may be comprised of any suitable material which would be familiar to those in the art having the benefit of this disclosure.

FIGS. 5 and 6 illustrate cross-sectional views of vacuum chuck 106 wherein gel material 404 including semi-solid particles 406 (See FIGS. 4 a and 4 b) replaces grinding protection tape 102 of FIG. 3 in one embodiment. In the embodiment, gel material 404 may be applied to upper surface 105 of wafer 104. In other embodiments, gel material 404 may be applied to platform 114 of vacuum chuck 106. For the embodiment, in order for wafer 104 to be held securely in place by gel material 404 to vacuum chuck 106, vacuum chuck 106 may not be activated. For the embodiment, gel material 404 may be able to protect wafer 104 by absorbing pressure, force, and vibration that grinding protection tape, such as grinding protection tape 102, of FIGS. 1-3 would normally absorb.

FIG. 6 shows that, in one embodiment, when vacuum chuck 106 is activated, gel material 404 may be substantially pulled off upper surface 105 of wafer 104 to allow gel material 404 to release wafer 104 from vacuum chuck 106. In the embodiment, vacuum 308 may be applied in a downward direction through porous material 304 of vacuum chuck 106. Thus, for the embodiment, wafer 104 is removed from vacuum chuck 106 by reducing surface contact between gel material 404 and upper surface 105 of wafer 104. Note that in various embodiments, gel material 404 may be of a pliable consistency and may hold various types of wafers including flip-chip bump and non-bump wafers without damaging surface structures on the wafer.

FIGS. 7 and 8 illustrate wafer grinding and dicing processes without the use of grinding protection tape 102 in embodiments of the invention. FIG. 7 shows a wafer grind-before-dice process but with the use of gel material 404 rather than grinding protection tape 102, in one embodiment. Resultantly, the process may be simplified as compared to the grind-before-dice process shown in FIG. 1. In the embodiment shown in FIG. 7, wafer 104 may be positioned face-down onto vacuum chuck 106 so that gel material 404 may be between platform 114 and upper surface 105 of wafer 104 to maximize or provide substantial surface contact between gel material 404 and upper surface 105. For the embodiment, in order for gel material 404 to hold wafer 104 in place, vacuum chuck 106 may not be activated as grinding chuck 108 grinds lower surface 109 of wafer 104. Once the grinding is finished, wafer 104 may be released from vacuum chuck 106 by activating vacuum chuck 106. In the embodiment, surface contact between gel material 404 and upper surface 105 of wafer 404 including any surface structures of wafer 404 may be reduced. Wafer 104 may then be mounted with wafer mount tape 112. In another embodiment, a vacuum transfer arm or device may be used to transfer wafer 404 from vacuum chuck 106 onto a mounting surface. Wafer 104 may then be diced at 116 into separate integrated circuit die or a plurality of integrated circuit die. Wafer 104 may also be washed before grinding and at various stages in the embodiment. In the embodiment, the process is simplified as the taping and de-taping processes of FIGS. 1 and 2 may be eliminated.

FIG. 8 illustrates one embodiment of the dice-before-grind method including the use of gel material 404 rather than grinding protection tape 102 of the process shown in FIG. 2. In the embodiment, wafer 104 may be partially diced at 116 to a depth slightly deeper than a final desired wafer thickness. Gel material 404 may be applied to upper surface 105 (see FIG. 5) of wafer 104 which is then positioned on vacuum chuck 106 to allow gel material 404 to hold wafer 104 against platform 114 of vacuum chuck 106. Vacuum chuck 106 is not activated as grinding chuck 108 grinds lower surface 109 of wafer 104 in the embodiment. In the embodiment, gel material 404 may absorb the type of grinding force, pressure, and vibration that a grinding protection tape such as grinding protection tape 102 normally would. When wafer 104 is thinned to a desired thickness, vacuum chuck 106 may be activated to allow gel material 404 to release wafer 104 from platform 114 of vacuum chuck 106. For the embodiment, semi-solid particles 406 (see FIG. 4 b) within gel material 404 may form a structure to substantially prevent the gel membrane surface from collapsing to vacuum chuck 106 when the vacuum chuck is activated. Wafer 104 may then be mounted with wafer mount tape 112. In one embodiment, wafer 104 may remain or rest on platform 114 of vacuum chuck 106 until wafer 104 may be mounted with wafer mount tape 112.

Thus, it can be seen from the above descriptions, one or more novel methods for semiconductor wafer grinding without the use of grinding protection tape have been described. While the present invention has been described in terms of the foregoing embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described. The present invention can be practiced with modification and alteration within the spirit and scope of the appended claims.

Thus, the description is to be regarded as illustrative instead of restrictive on the present invention. 

1. A method, comprising: applying an adhesive gel material to at least a portion of a first side of a semiconductor wafer having first and second sides; positioning the semiconductor wafer on to a platform with the first side facing the platform and with the adhesive gel material between the first side and the platform to allow the adhesive gel material to hold the semiconductor wafer to the platform; grinding the second side of the semiconductor wafer; and allowing the adhesive gel material to release the semiconductor wafer from the platform.
 2. The method of claim 1 wherein allowing the adhesive gel material to hold the semiconductor wafer to the platform comprises using an adhesive property of the adhesive gel material to hold the semiconductor wafer to the platform.
 3. The method of claim 2, wherein the platform includes a vacuum, and wherein using the adhesive property to hold the semiconductor wafer to the platform includes holding the semiconductor wafer in position using the adhesive gel material with the vacuum substantially turned off.
 4. The method of claim 2 wherein using the adhesive property to hold the semiconductor wafer to the platform includes providing substantial surface contact between the adhesive gel material and the first side of the wafer.
 5. The method of claim 1, wherein allowing the adhesive gel material to release the semiconductor wafer from the platform includes applying a vacuum to the gel material to substantially pull the adhesive gel material off the first side of the semiconductor wafer.
 6. The method of claim 1 wherein applying the adhesive gel material to at least a portion of the first side of the semiconductor wafer includes applying the adhesive gel material to an upper surface of an un-diced semiconductor wafer.
 7. The method of claim 6, further comprising after grinding the second side of the semiconductor wafer, which comprises a lower surface of the semiconductor wafer: washing the semiconductor wafer; mounting the semiconductor wafer; and dicing the semiconductor wafer.
 8. The method of claim 1, wherein applying the adhesive gel material to the first side of the semiconductor wafer includes applying the adhesive gel material to an upper surface of at least a partially-diced semiconductor wafer.
 9. The method of claim 8, further comprising after grinding the second side of the semiconductor wafer, which comprises a lower surface of the semiconductor wafer, mounting the semiconductor wafer that has had its lower surface grinded.
 10. The method of claim 1, wherein applying the adhesive gel material to the first side of the semiconductor wafer includes applying the adhesive gel material to an upper surface of a flip chip bump wafer or non-bump wafer
 11. The method of claim 1 wherein applying the adhesive gel material includes applying a gel material including semi-solid particles.
 12. The method of claim 11 wherein allowing the adhesive gel material to release the semiconductor wafer from the platform includes applying a vacuum to draw the membrane away from the first side of the semiconductor wafer
 13. The method of claim 1 wherein applying the adhesive gel material to the first side of the semiconductor wafer includes applying the adhesive gel material to an upper surface of a semiconductor wafer having surface structures.
 14. The method of claim 13 wherein the surface structures include bumps.
 15. The method of claim 13 wherein the surface structures include electronic circuitry.
 16. A method, comprising: applying a gel material to a first side of a semiconductor wafer, having first and second sides, to provide substantial surface contact between the gel material and surface structures on the first side; placing the wafer on a vacuum chuck with the gel material between the wafer and the vacuum chuck; grinding the second side while using the gel material to hold the wafer against the vacuum chuck; and removing the wafer from the vacuum chuck by reducing surface contact between the gel material and the surface structures.
 17. The method of claim 16, wherein applying the gel material to the first side of the semiconductor wafer includes applying the gel material to a surface of at least one of a flip-chip bump wafer and a non-bump wafer.
 18. The method of claim 16 wherein the surface structures comprise electronic circuitry.
 19. The method of claim 16 wherein the surface structures comprise bumps.
 20. The method of claim 16 wherein reducing surface contact between the gel material and the surface structures includes activating the vacuum chuck.
 21. The method of claim 16 wherein the gel material includes semi-solid particles.
 22. The method of claim 16 wherein applying the gel material to the first side of the wafer includes applying a semi-solid material to an upper surface of the wafer, the semi-solid material capable to be prevent substantial collapse of a gel membrane of the gel material into the vacuum chuck.
 23. The method of claim 16, further comprising after removing the wafer from the vacuum chuck: washing the wafer; mounting the wafer; and dicing the wafer.
 24. The method of claim 16, further comprising dicing the wafer before applying the gel material to the first side of the wafer.
 25. The method of claim 24 wherein the wafer is diced to a depth deeper than a final desired depth of the wafer.
 26. The method of claim 16, further comprising using a vacuum transfer device to transfer the wafer from the vacuum chuck onto a surface for mounting.
 27. The method of claim 16 wherein grinding the second side of the wafer while using the gel material to hold the wafer against the vacuum chuck includes absorbing at least some of a grinding force applied to the second side of the wafer.
 28. A material, comprising: an adhesive gel material; semi-solid particles within the adhesive gel material; and wherein the adhesive gel material forms a membrane surface to hold a first side of a semiconductor wafer to a surface of a vacuum chuck during wafer grinding of a second side of the semiconductor wafer.
 29. The material of claim 28 wherein the semi-solid particles within the adhesive gel material form a structure to substantially prevent the membrane surface from collapsing to the surface of the vacuum chuck when the vacuum chuck is activated.
 30. The material of claim 28 wherein the semi-solid particles within the adhesive gel material includes organic particles. 